Certain physiological impairments appear with age, seasonal variations, stress and atmospheric attacking factors. They include in particular a reduction in hair density during aging, the number and diameter of the hair stems decreasing. In particular, certain individuals develop alopecia.
To prevent hair impairments that appear mainly with age, use has been made hitherto of essential amino acids, which are recognized as being vital as nutrients for the synthesis of keratin in the hair bulb. Thus, methionine, cystine and cysteine are known to have a direct impact on the metabolism of the hair follicle. However, these essential amino acids act on protein synthesis, which is not the only mechanism involved in the phenomenon of alopecia.
Among the causes of alopecia, it has in fact been determined that impairment of the perifollicular connective tissue was reflected by rigidification of the connective sheath, which is thought to explain the miniaturization of the hair follicle, a sign of aging of the pilosebaceous unit.
Furthermore, these impairments in the hair are often accompanied by impairment in the condition of the scalp, such as the abundant production of sebum. Hypersecretion of sebum or seborrhea and its consequences, for example acne, often appear during puberty, but may continue into adulthood, especially in women, for hormonal reasons.
These disorders may occur in combination, to varying degrees, in the same individual.
To combat alopecia, which characterizes the hair follicle, it has been recommended to use medicinal products that inhibit collagen metabolism. It is known practice especially to use minoxidil, and, at the present time, the mechanism of action of minoxidil, which is known to be able to combat the process of miniaturization of the hair follicle, without being anti-androgenic, is still unknown.
To combat the hypersecretion of sebum, local treatments have been proposed, including isotretinoin, but this treatment is not without serious side effects.
It has also been recommended to use antiandrogens against alopecia and hypersecretion of sebum, via the systemic route. However, this type of treatment is not without serious side effects, in particular on the sexual organs.
For its part, document WO 99/22728 describes numerous compounds, including fatty acids, especially for therapeutic uses. However, the medicinal products have drawbacks associated with the risks inherent in their use, insofar as the medicinal products are xenobiotics. In addition, the medicinal products generally have a highly targeted spectrum of action, whereas the causes of impairment of the pilosebaceous unit are manifold.
Moreover, taurine is described as being a cellular activator for regulating hair cells and is proposed in hair-stimulating compositions for topical application, in document WO 02/24189. However, the taurine used as topical cellular activator has limited effect due to the fact that the loss of cellular activity may be caused by several factors of alopecia. If these factors persist, the temporary effects of a topical application of a cellular activator are limited. Furthermore, compositions for topical use have for their part drawbacks associated with local application. The frequency of the applications is generally higher and the application of these compositions to a large area to be treated may require a certain amount of time.
It has thus been found that there is still a need for active agents that can be administered orally, which are effective in the treatment and/or prevention of the signs of aging of the hair and/or functional disorders of the pilosebaceous unit, and especially alopecia, and which are free of side effects. The pilosebaceous unit comprises a hair follicle and its sebaceous gland.